When MySQL is slow
alter table
mysql alter table is to slow
mysql> ALTER TABLE OPERA_ORATORIO ADD nseq_length smallint
-> ;
Query OK, 15048730 rows affected (3 hours 8 min 3.72 sec)
Records: 15048730 Duplicates: 0 Warnings: 0
as the answer said, better to create new table to replace the old one http://stackoverflow.com/questions/12774709/mysql-very-slow-for-alter-table-query